Pass a long. Set close to 1 to make libcurl explicitly close the
connection when done with the transfer. Normally, libcurl keeps all
connections alive when done with one transfer in case a succeeding one follows
that can re-use them. This option should be used with caution and only if you
understand what it does as it can seriously impact performance.

Set to 0 to have libcurl keep the connection open for possible
later re-use (default behavior).